The present invention is directed to controlling flight control surfaces in aircraft, and more particularly to an actuator system that controls the position of a flight control surface.
Control over aircraft flight control surfaces is critical to proper steering of the aircraft. Hydraulic actuators have long been used to modify the positions of flight control surfaces. Most systems couple each flight control surface with multiple actuators so that an operator can still control the surface, and therefore maintain safe control over the aircraft, even if one of the actuators fail.
As is known in the art, hydraulic actuators can be disabled if a malfunction is detected. To preserve flight control surface control, the malfunctioning hydraulic actuator can be put into a bypass mode where the actuator moves freely as the remaining actuators in the control system continue to move the flight control surface. The malfunctioning actuator is then driven by the remaining operational actuators.
Other types of actuators, however, may have structures that prevent any movement of the actuator during a malfunction, such as a jam or hardover failure. For example, actuators that are built with geared elements may lock the actuator into an undesired position if debris enters the actuator or if components within the actuator move out of their proper aligmnents. Because malfunctions in other types of actuators may lock the actuator into a position during malfunction, the remaining actuators cannot move the flight control surface to compensate for the malfunction. Further, some actuator types do not have a bypass mode that allows the actuator to be driven or otherwise movable during malfunction because it is not possible to dislodge the malfunctioning actuator from its locked position. The malfunctioning actuator therefore causes the flight control surface to seize. If the flight control surface seizes in a position other than in a neutral position, the aircraft may be difficult to handle. As a result, only limited types of actuators are considered appropriate for controlling flight control surfaces.
There is a desire for a flight control surface control system that can accommodate different types of actuators even if they lock up during malfunction.
The present invention is directed to a flight control surface actuation system having a plurality of actuators attached to one or more levers so that the lever orientation dictates the flight control surface position.
In one example, each lever is attached to the flight control surface at an actuator output point on the lever. The lever orientation dictates the position of the flight control surface and corresponds with a sum of the positions of the actuators attached to it. Thus, the flight control surface position is controlled by the lever position rather than directly via the actuator position.
If one of the actuators malfunctions in a way that locks the actuator in a certain position, the inventive system can still move the flight control surface by moving other actuators attached to the same lever as the malfunctioning actuator to compensate. Thus, the flight control surface can always be moved to a safe, neutral position even if a malfunctioning actuator locks in an extreme extended or retracted position. The lever makes it possible for flight control surface actuation systems to use a wider variety of actuators, including actuators that do not have a bypass mode.